Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$101.25	12.710%	$114.1189	$114.12	$114.10	$114.10
Purchase #2	$109.42	13.588%	$124.288	$124.29	$124.30	$124.30
Purchase #3	$115.46	10.140%	$127.1676	$127.17	$127.15	$127.20
Purchase #4	$201.92	8.681%	$219.4487	$219.45	$219.45	$219.40
Purchase #5	$215.31	3.612%	$223.087	$223.09	$223.10	$223.10
Purchase #6	$101.90	7.656%	$109.7015	$109.70	$109.70	$109.70
Purchase #7	$61.66	4.781%	$64.608	$64.61	$64.60	$64.60
7 purchase totals =	$906.92		$982.4197	$982.43	$982.40	$982.40